Method of removing ketones from fatty acids



United States Patent Ofifice 2,715,642 Patented Aug. 16, 1955 METHOD OF RED'IOVING KETQNES FROM FATTY ACIDS George Barsky, New York, N. Y., assignor to E. F. Drew & Co., Inc., New York, N. Y., a corporation of Delaware No Drawing. Application April 17, 1951, Serial No. 221,521

2 Claims. (Cl. 260-419) The present invention is directed to the purification of as those present as glycerides in animal and vegetable oils in suitable esterification kettles for the purpose of producing esters for industrial and edible purposes. In the course of such an operation, which is conducted at relatively high temperatures, vapors of fatty acids arise and are condensed outside of the reaction vessel. densed fatty acids are quite impure, often being dark colored and having unpleasant odors. The objectionable impurities consist essentially of ketones, some of which may be formed under the conditions of esterification. Such acids usually cannot be reused as such and are of relatively little value, constituting a waste material. It has been proposed to refine the same by fractional distillation under special conditions but the operation is not satisfactory. The impurities are only partially removed and it is dimcult to prevent the re distilled acids from becoming colored in the distillation. Furthermore, the operation is expensive, both from the standpoint of the necessity of providing a complicated equipment and the supervision necessary in conducting the distillation. Such a procedure entails very substantial losses of fatty acids.

The present invention is intended and adapted to overcome the difliculties and disadvantages inherent in the prior art, it being among the objects thereof to provide a method of treatment of impure fatty acids containing I ketones, which is simple in operation and highly eifective for the removal of various impurities including said ketones.

It is also among the objects of the present invention to provide a process of refining such impure fatty acids which avoids any distillation step, which requires only inexpensive simple equipment and wherein the processing cost is low and the losses of material are practically negligible.

It is further among the objects of the present invention to provide a single stage operation wherein a direct reaction occurs with one of the constituents, whereby it is automatically separated from the other constituent and may be readily removed to complete the purification of the fatty acids.

In practicing the present invention, there is provided a fatty acid or a mixture of fatty acids which are substantially insoluble in water. Usually such acids have at least 6 carbon atoms and may have as high as 22 carbon atoms. Such fatty acids are the by-product of an esterification reaction conducted at elevated temperatures and contain ketones, said ketones rendering the fatty acids unusable directly for many purposes. Such fatty acids may be obtained from the reconstruction of glyceride oils of the coconut type, wherein lower fatty acids are displaced by higher fatty acids and are removed by volatilization.

The con- 1-.

The impure fatty acids are treated with a compound which is capable of reacting with one or the other of the constituents, namely either the fatty acid or the ketone, to form a reaction product which is insoluble in the other constituent of the impure fatty acid. Thereby a direct separation takes place and if the reaction product is a liquid or a solution, two layers are formed on standing. Separation of the layers may be obtained by the usual well-known methods.

The invention contemplates two types of reaction, in one of which the fatty acid is reacted to form a watersoluble compound such as a soap. Various bases usually in water solution are used for the reaction. It is caused to take place with the application of heat although generally below the boiling point of water. After the reaction is complete, the mixture is allowed to settle into two layers, one of which is an aqueous soap solution and the other consists of the ketones and other impurities. In another type of reaction a substance is introduced into the impure fatty acids which combines with the ketones to form a product insoluble in the fatty acids. Such substance may be in organic, such as acid sulphites, or may be of organic nature. The products of this type of reaction are generally considered to be addition products, some of them being crystalline so that they precipitate out of the fatty acids, leaving them in a pure state.

The following are specific examples of the operation of the invention:

Example I impure fatty acids of the above described type, consisting largely of fatty acids having 6, 8 and 10 carbon atoms, are placed in a suitable reaction vessel, such as a kettle equipped with a stirrer and means for heating the same. An 8% aqueous solution of sodium hydroxide is added to the fatty acids while stirring, the amount so added being suflicient to provide a soap solution, after all of the fatty acids have been saponified, of a strength of about 20% to 30%. It is highly desirable that the resulting soap solution be not too concentrated as the mass becomes quite viscous and the refining is incomplete. The soap solution should not be too dilute as it is too bulky to handle conveniently and difliculties are encountered at a later stage in the recovery of the fatty acids therefrom.

While stirring the mixture the temperature is raised to 6080 C. and the reaction allowed to take place over a. period of one to two hours in order to convert the fatty acids into a soap. While maintaining the elevated temperature, agitation is stopped and the reaction mass allowed to settle for several hours. Two layers are formed, the upper oily layer containing the impurities and the lower layer consisting of the soap solution.

The upper layer is removed and recovered. The lower soap layer is treated with an acid such as sulphuric acid in sufiicient amount to combine with all of the sodium present in the soap. This releases the free fatty acids which may be recovered in the usual manner.

Example 2 To the impure fatty acids there is added an amount of triethanolamine calculated to be suflicient to combine with all of the fatty acids in the starting material. The mixture is stirred and heated to about 45 C. After about 15 minutes, Water is added to the reaction mass and stirring and heating are continued for about one hour. The amount of water added is sufficient so that the triethanolamine soap formed in the reaction is in a concentration of 20 to 30%.

The reaction now being complete, the stirrer is stopped, the temperature is reduced to about room temperature and the mass is allowed to stand for several hours. The

' constituents separate into two layers, the lower water layer consisting of the soap and the upper layer consisting of the impurities. The latter are removed by decantation and the soap solution is acidified for the recovery of the free fatty acids.

There are numerous advantages inherent in the'present invention. The method is simple and highly efiective so that there is recovery both of the fatty acids and of the ketones with practically negligible losses; The fatty acids so obtained'are' sufliciently pure that they may be used for edible purposes, as for example, in the making of a hard butter. used for industrial'purposes such as in the making of esterj plasticizers for synthetic resins. In. the latter use the plasticizer shows a lower volatile loss and a greater freedom from color. The refined fatty acids are practically water-white and this is highly desirable in the art for use in various chemical reactions. The equipment is simple and inexpensive. The operation can be conducted by relatively unskilled labor and it is a single step operation which is highly economical.

' Although the invention has been described setting forth several specific embodiments thereof, the examples are intended to illustrate the invention and not to limit it as many variations in the details may be made within the spirit of the invention. For instance, in place of the caustic soda, other alkalis may be used such as potassium or ammonium hydroxides or bicarbonates or carbonates of .the alkali metals. The base used maybe of organic nature and may be aromatic amino compounds, cyclic nitrogen compounds or aliphatic amines. The conditions of the operation may be varied within certain limits, as for example, the concentrations of the solutions may be different than those specifically stated. Other temperatures may be applied and the time elements may be The color is light, and they may be varied to a considerable degree. be conducted such as a bleaching operation after the recovery of the fatty acids or a filtration through earth or the like.

Other reagents capable of combining with the ketones may be used such as other alkali. metal acid sulphites. The impure acids treated by the present method need not necessarily come from animal or vegetable oils but any carboxy acids from whatever source and containing ketones to be removed are amenable to the present process. a

I claim: V

l. A method of purifying fatty acids containing ketones as impurities which comprises providing a fatty acid substantially insoluble in water and containing ketones, adding an alkylolarnine thereto, agitating and heating the' mixture, adding thereto a suflicient amount of water to form a 20-30% soap solution, then allowing the mixture to separate into two layers, removing the soapfrom said ketones.

2. A method of purifying fatty acids containing ketones.

as impurities which comprises providing a fatty acid substantially insoluble in water and containing'ketone's, adding triethanolamine thereto, agitating and heating the mixture, adding thereto a sufiicient amount of water to form a 20-30% soap solution, then allowing the mixture to separate into two layers,'removing the soap from said ketones.

References Cited in the file of this patent V UNITED STATES PATENTS Bang Dec. 25, 1883 Other operations may 

1. A METHOD OF PURIFYING FATTY ACIDS CONTAINING KETONES AS IMPURITIES WHICH COMPRISES PROVIDING A FATTY ACID SUBSTANTIALLY INSOLUBLE IN WATER AND CONTAINING KETONES, ADDING AN ALKYLOLAMINE THERETO, AGITATING AND HEATING THE MIXTURE, ADDING THERETO A SUFFICIENT AMOUNT OF WATER TO FORM A 20-30% SOAP SOLUTION, THEN ALLOWING THE MIXTURE TO SEPARATE INTO TWO LAYERS, REMOVING THE SOAP FROM SAID KETONES. 